Water runs through it

Reduce runoff with hardscape options that redirect rainwater into the ground

A new fountain at the Water Conservation Garden at Cuyamaca College is surrounded by permeable concrete, which allows rainwater or irrigation to soak through to the soil. The garden showcases water-wise hardscaping options.
— Nelvin C. Cepeda

A new fountain at the Water Conservation Garden at Cuyamaca College is surrounded by permeable concrete, which allows rainwater or irrigation to soak through to the soil. The garden showcases water-wise hardscaping options.
— Nelvin C. Cepeda

The garden’s newest exhibit, funded by the county’s Watershed Protection Program, showcases concrete that’s less dense than standard concrete, a mix of aggregates and cement. The use of larger aggregates minus small gap-filling “fines” creates a permeable surface that water passes through.

Not as tough as concrete, permeable concrete is best for walks, patios and light-traffic roads, Sherman says. (Driveways can be problematic, depending on their slope and the weight of vehicles parked there.) Aesthetically, permeable concrete resembles hand-seeded concrete where the aggregate is exposed, rather than hidden under smooth cement. “It’s a custom look, but not one everybody likes,” Sherman says.

Compared with standard concrete, permeable concrete costs about 15 percent to 20 percent more, Sherman notes. In new construction, that increase often is offset by reduced need for other more expensive drainage solutions. For this and all other permeable pavement options, Sherman emphasizes the need for proper site selection and preparation. Pouring and finishing concrete is not a DIY project — consult with a landscape architect or designer and have the installation done by an experienced licensed contractor.

Below are some other permeable paving options. “All of these can be used creatively in a million different ways and combinations to be environmentally friendly,” Sherman says.

Gravel: Used for centuries, washed and cleaned crushed rock is a highly permeable ground cover as well as surface for patios, paths, driveways and access roads. Avoid rounded pebbles because “you sink when you walk on them,” Sherman says. “But if you like to walk barefoot, sharp-edged gravel isn’t for you.” This stone is available in “every color, shape and size imaginable,” he adds. Cost: One of the least expensive options.

Permeable pavers: These pavers of stone or concrete have clipped corners or cutouts that are filled with sand to allow water to seep into the ground. Set on a bed of sand with no concrete seams. Available in a variety of designs and colors. Useful for driveways, parking areas, paths or patios.

Cost: Equivalent to concrete.

“All paving requires an adequately prepared base and may benefit from a filter fabric layer below,” Sherman notes. “And both DG and gravels should be installed 2 to 6 inches, deep depending on the intended use.”